Optocouplers are often used to provide galvanic isolation between different voltage sources in an electronic circuit. Functions of optocouplers include providing high voltage package isolation and isolating noise of a main signal from a resulting signal. In an electronic circuit, an optocoupler ensures electric isolation. For example, optocouplers are used in applications such as telecommunications equipment, programmable controllers, direct current (DC) to DC converters, switch-mode power supplies, alternating current (AC) to DC converters and battery chargers. Optocouplers are disclosed and discussed in Vishay Telefunken, “General Description Basic Function”; Vishay “Optoelectronics”; Mikami et al., U.S. Pat. No. 4,614,958; Brown, U.S. Pat. No. 5,150,438; and Gempe et al., U.S. Pat. No. 6,013,251, the disclosures of each of which are hereby incorporated herein by reference.
An optocoupter may be considered comparable to a transformer or relay in some cases. However, optocouplers are typically smaller, ensure considerably shorter switching times, eliminate contact bounce, eliminate interference caused by arcs, and do not experience mechanical wear. Thus, optocouplers are particularly well suited for circuits used in microelectronics and also in data processing and telecommunication systems. Optocouplers are also used to promote component safety, such as in switch-mode power supplies.
In practice, a control circuit or the like is typically located on one side of the optocoupler, for example the emitter side, while a load circuit is located on the other side, the detector side in this example. The circuits are electrically isolated from each other by the optocoupler. Signals from the control circuit are transmitted optically to the load circuit, and are therefore free of reciprocal effects.
In most cases, optical transmission by an optocoupler employs light beams with wavelengths spanning from the red to infrared range. The bandwidth of signals transmitted by an optocoupler typically range from a DC voltage signal to frequencies in the MHz band, although signal frequencies in the GHz range are possible.
FIG. 1 shows an optocoupler configuration representative of the majority of optocoupler packages found today. As shown in FIG. 1 optocoupler package 100 defines light emitting device or diode (LED) 102 directly above detector 104 separated by generally transparent insulating material 109. Also shown in FIG. 1 for completeness are lead 103 coupled to LED 102 and lead 106 coupled to detector 104 by bond wire 105. Leads 103 and 106 provide signal communication between components of optocoupler package 100 and those external thereto, such as devices disposed upon printed circuit board 101.
In the above conventional configurations, the package height is limited by at least the sum of the device heights (height of LED 102 plus the height of detector 104), with additional material such as transparent insulating material 109 and mold compound 107 required to complete the package adding to the package height. However, as today's electronic applications become more and more complex and integrated, there is a continuing need to reduce component package size without sacrificing functionality. This becomes more challenging with the emergence of notebook computers, personal digital assistants (PDA), cellular telephones, and the like.
FIG. 2 shows an optocoupler package configuration representative of those described in U.S. Pat. Nos. 5,150,438 and 6,031,251, referenced above. Specifically, shown in FIG. 2 is an in-line or coplanar arrangement for optocoupler package 200, providing a reduced optocoupler profile or height (although this configuration may have a larger substrate footprint than optocoupler package 100 associated therewith). Such coplanar optocoupler packages typically employ a transparent insulation material 209 surrounding LED 202 and detector 204. Further, a reflective material 211, coating transparent material 209, is provided. Mold compound 207 incarcerates the components of optocoupler package 200. Also shown in FIG. 2 for completeness are lead 203 coupled to LED 202 and lead 206 coupled to detector 204 by bond wire 205. Leads 203 and 206 provide signal communication between components of optocoupler package 200 and those external thereto, such as devices disposed upon printed circuit board 201.
In the above linear configurations, although the optocoupler package height has been reduced over the more typical configuration discussed above, the package configuration experiences disadvantages. For example, the indirect or reflective light coupling of previous configurations often suffers from inefficiencies in the reflection of the light. Accordingly, a need for an effective, efficient, low profile optocoupler still exists in the art today.